A better understanding of the vertebrate olfactory system would provide improved means to manipulate this process and possibly prevent disease or injury. For example, means to manipulate human olfactory neuron odorant receptors from healthy individuals and from individuals with neuro-psychiatric illnesses would offer systems for testing possible odorant/ligands for therapeutic and toxic effects. However, our ability to detect and discriminate between the thousands of beneficial or toxic odorants is complicated by the fact that odorant receptors belong to a multigene family with at least 500 to 1000 members. Furthermore, each olfactory receptor neuron may express only one, or at most a few, of these olfactory receptors. Any given olfactory neuron cell can respond to a small, arbitrary set of odorant-ligands. Odorant discrimination for a given neuron may depend on the ligand specificity of the one or few receptors it expresses. Thus, given this systems' complexity, information about odorant/ligand-receptor recognition remains meager.
To analyze odorant/ligand-receptor interactions and their effects on cell physiology, it is first necessary to identify specific odorant/ligand(s) and the olfactory receptors to which they specifically bind. Such analysis requires isolation and expression of olfactory receptor polypeptides. However, despite the fact that many putative olfactory receptors have been cloned, only limited progress has been made in the functional expression of these receptors because present systems fail to efficiently translocate these 7-transmembrane proteins to the plasma membrane. This may be because olfactory receptors are a subclass of 7-transmembrane-domain receptors. For example, expression of one rat olfactory receptor in insect cells resulted in only a modest elevation in second messengers when exposed to a mixture of odorants; responses to single compounds were not seen (Raming (1993) Nature 361:353-356). The present invention addresses these and other needs.